An air cooling device for a driving system is mounted on an electrically powered contructional large size dump truck which are used in a mine, a quarry and so forth. The cooling device has an air intake at the front side of the vehicle. An air introduced through the air intake is fed to a generator, drive control device and a motor through an air passage for cooling the driving system.
As shown in FIGS. 8 and 9, the cooling device is provided with an air cleaner within an air intake 1 for separating a dust, such as a sand or so forth and rain water from the air for feeding only air to the downstream. Conventionally, a louver array 6 is employed in the air cleaner. A plurality of louver arrays 6 are provided within the air intake 1 in such a manner that distances thereof are narrowed toward the downstream side. Dust shoots 7 are provided between the narrowed ends of the louver arrays 6. The air introduced from the front side of the vehicle, i.e. from an air inlet side flows into spaces between the louver arrays 6. The air flows through gaps in the louver arrays 6 toward downstream. On the other hand, the dust and rain water are guided into the dust shoots 7 by the louver arrays 6 and fall down in the dust shoots 7. The dust and rain water are then externally discharged through a dust discharge valve 8.
In the driving system cooling device mounted in the electrically powered contructional large size dump truck, the conventional air cleaner tends to permit fine particle dust and rain water to pass through the gaps in the louver arrays together with the air to penetrate into the cooling device to reach the generator, the drive control device and motor of the driving system to lower electrical insulation performance of the driving system to cause damage.
On the other hand, as disclosed in Japanese Examined Patent Publication (Kokoku) 54-4106, there has been proposed a swirl flow type air cleaner formed by assembling a plurality of small diameter tubular bodies, preferably having a diameter less than or equal to 5 cm. However, since the air cleaner for the cooling device of the drive system of the large size dump truck requires a huge capacity, especially as a machine for mines, for low cost and long duration, a large number of small diameter tubular bodies should be used for unacceptably lowering cost-performance. Furthermore, when such a large number is introduced into the small diameter tubular bodies, air induction resistance becomes substantially high, thus causing a lowering of a dust separation performance.
Also, Japanese Unexamined Patent Publication (Kokai) No. 57-56657 proposed a swirl flow type pre-cleaner of a thin panel type which is provided on the top of an element type air cleaner. The disclosed cleaner has mutually opposite vane angles of a swirl type air inlet which are provided at left and right side vanes to generate a gear type swirling flow so as not to disturb laminar flow of the air. The shown arrangement is effective in separating relatively large particle sizes of dust. However, because of a substantially short axis distance of the swirl flow layer of the air, difficulty is encountered in separating fine particle dust. Therefore, the structure must be followed by a pleated type air filtering element at the subsequent filtering stage. Moreover, the pleated type air filtering element requires regular replacement, thus increasing the cost. In addition, when a large amount of air is to be introduced, the intake air flow resistance becomes substantially large to lower dust separation performance.
Japanese Examined Patent Publication No. 57-38302 proposed an air cleaner of the type in which a large spiral type air flow is generated. However, in the shown construction, a rain water eliminating cap may cause a lowering of installation density. On the other hand, when the rain water eliminating cap is removed for higher installation density, bends at the air inlet and outlet may cause a swirling flow of the air at the air inlet and outlet of the element to affect uniform induction of the air to lower the air induction efficiency.